| Subacute ruminal acidosis (SARA) is a common metabolic disease and over20%cows during lactation are diagnosed as SARA in intensive dairy herds. SARA could induce an intestinal flora disturbance, laminitis, liver abscess. As a result, these adverse changes will alter the milk composition, and even have serious effects on the health and productivity of the dairy cows. Studies on SARA have mainly focused on the alterations of biochemical parameters in blood and diagnosis of SARA. Unfortunately, the changes of immune function in liver when ruminants suffered SARA are poorly understood. This study focused on the changes of lipopolysaccharide (LPS) content, which was largely produced in rumen during SARA, as well as some factors regulated with toll-like receptor4(TLR4) signalling pathway in liver to reveal the effects of SARA on immune function of liver, which would cause the metabolic disturbance in the liver.1Effect of SARA on immune function of liver and appetite regulating factors in hypothalamus of non-lactating goatsTwelve healthy non-lactating Chinese local goats (15-20kg) were selected and were randomly allocated to two groups and fed with different concentrate to roughage ratio diets with60:40(SARA group) and40:60(control group), respectively. Goats were free access to water. The experiment lasted for3weeks. At the end of the experiment, the rumen fluid, blood, hypothalumus and liver tissues were collceted. pH in rumen fluid was determined immediately after the sampling. Then the concentration of cytokines such as TNF-a, IL6, IL-1and acute phase proteins (APPs) such as LBP, HP, SAA in plasma were detected. Genes expression of TLR4-related factors, cytokines, APPs in liver and factors involved in appetite regulation in the hypothalamus were determined with real-time PCR.Results showed:SARA disease was successfully induced in dairy goats feeding a diet with roughage to concentrate ratio of40:60(SARA group); pH of rumen fluid of SARA group was below5.8and lasted for more than3hours, while ruminal pH in control group was above6.0.(2) Concentration of lactate in rumen fluids were decreased during2-4hour after feed delivery and increased during6-8h with no significant difference between two groups (P>0.05).(3) Concentration of IL-1β and HP of SARA group was significantly higher than that of control (P<0.05), while concentration of TNF-a in blood of SARA goats showed a trend to increase (0.05<P<0.1).(4) SARA had no significant effect on gene expression of TLR4and cytokines in liver (P>0.05), but significantly up-regulated mRNA transcription of SAA and HP in liver (P<0.05).(5) Compared with control goats, genes expression of TLR4, MyD88and TNF-a in hypothalamus were significantly up-regulated in SARA goats (P<O.05). In the hypothalamus, AgRP mRNA expression was markedly decreased (P<0.05) in SARA goats and NPY mRNA transcription showed a tendency to derecease in SARA goats compared to the control goats (0.05<P<0.1).2Effect of SARA on lactation performance and immune function of liver in mid-lactating goats(1) Short-term experiment:Seven healthy mid-lactating Chinese local goats were selected in a2×2Latin square experiment design and were randomly allocated to two groups fed with different concentrate to roughage ratio of60:40(SARA group) and40:60(control group), respectively. Goats were free access to water. The experiment lasted for14days. The value of pH in rumen fluids was determined immediately after sampling. Concentration of lactate in rumen fluids was also determined by commercial kits. Concentrations of LPS and cytokines such as TNF-a, IL-1β, IL-6in plasma were also detected by biochemical methods. Genes expression of TLR4and related cytokines were measured with real-time PCR.Results:Feeding a diet with roughage to concentrate ratio diet of40:60for14days successfully induced SARA in goats during mid-lactating (SARA group). The value of pH in rumen fluids of SARA goats was below5.8and lasted about6hours after feeding. The concentrations of LPS and lactate in rumen fluids of SARA group were significantly higher than that in control goats (P<0.05). SARA had an significant effect on plasma level of TNF-a and IL-1β (P<0.05), while there was no significant difference in gene expression of TLR4, TNF-a and IL-1β in liver between two group goats (P>0.05). SARA caused the accumulation of lactate and the increase of LPS in rumen fluids (P<0.05), but did not affect the genes expression of TLR4and related cytokines when lactating goats suffered a short-term SARA (P>0.05).(2) Long-term experiment:Eight healthy mid-lactating dairy goats were selected and were randomly allocated to two groups and fed with different concentrate to roughage ratio diets of60:40(SARA group) and40:60(control group), respectively. The experiment lasted for9 week. The results showed that:(1) pH in rumen fluids of SARA goats was below5.8for4h at2wk and increased slightly from4to9wk, but still significantly higher than that in control group (P<0.05). Concentration of lactate in rumen fluid had a trend to increase (0.05<P<0.1). The concentration of LPS in rumen fluids did not show significant difference between two group goats (P>0.05).(2) Milk yield of SARA goats was lower than that of control group (P<0.01), the level of lactoprotein and butterfat was significantly lower than that of control during6-9wk (P<0.05). Content of lactose of SARA goats was significantly lower than that of control and Somatic cell count of SARA group was higher at8wk.(3) Compared to control goats, concentration of TNF-a in plasma of SARA group increased significantly, while the content of IL-6in plasma had a trend to increase. Moreover, plasma concentration of SAA increased significantly and content of HP had a trend to increase in SARA goats (P<0.1).(4) SARA significantly up-regulated the genes expression of TLR4, IL-1β and CRP, HP and SAA in liver (P<O.05). |
PDF Full Text Request